JP-2005-045217A (US 2004/0257185 A1) discloses a linear solenoid mounted to a vehicle outputs a thrust using a magnetic flux generated according to an energization of a coil.
In the linear solenoid, a movement amount of a movable core in an axial direction can be increased without increasing a size of the linear solenoid in the axial direction. The movable core includes a cylindrical portion. Stator cores are placed at positions inside of the movable core and outside of the movable core, respectively.
A better configuration of the linear solenoid according to JP-2005-045217A includes the movable core, a first stator core, a second stator core, and a third stator core, which are made of magnetic material.
The movable core includes a magnetic portion having a cylindrical shape, and is placed in an inner periphery of the coil and is movable with respect to an axial direction concentric with the coil. The first stator core is placed at a position inside of an inner periphery of the movable core, and the first stator core receives and transmits the magnetic flux in a radial direction of the movable core. The second stator core is a magnetic portion having a cylindrical shape, and is placed at a position outside of an outer periphery of the movable core such that the movable core is interposed between the first stator core and the second stator core. The second stator core receives and transmits the magnetic flux in the radial direction of the movable core. The third stator core is placed at a position such that the third stator core is not in contact with the second stator core in the axial direction. The third stator core magnetically attracts the movable core in the axial direction.
However, the first stator core, the second stator core, and the third stator core can be directly positioned in the radial direction.
According to JP-2005-045217A, a magnetic portion provided integrally with the first stator core and a magnetic portion provided integrally with the second stator core are fitted to each other to position the first stator core and the second stator core in the axial direction.
Therefore, the first stator core, the second stator core, and the third stator core is insufficiently positioned in the radial direction, and it is possible that a side force generated by an axis deviation between the first stator core, the second stator core, and the third stator core increases. In this case, the side force is an attractive force generated between the movable core, the first stator core, the second stator core, and the third stator core, in the radial direction.